This chart represents the returns of a 117 different $1 million portfolios with no withdrawals over the course of 30 years. Each line represents historical outcomes for the same portfolio (to the extent possible), with an allocation of 50% each between equities and fixed interest.

The only difference between each of the 117 portfolios? When the portfolio began. Ie, one of those lines relates to a 30 year period starting in 1900. One relates to a period starting in 1929. One in 1967. 1980. Etc.

FIREcalc shows historical returns dating back to 1871. Some caveats: it’s US-focused. And of course, historical returns are no guarantee of future returns.

But despite these qualifications, this graph illustrates something we need to take to heart: we just can’t know ahead of time how investments will perform.

I wish I could predict returns. I wish I could provide certainty.

I wish I could be able to pick which line an investment portfolio will follow. But I can’t. I don’t think anyone can. And to tell anyone otherwise is a disservice.

If someone says they can tell you what you’ll get – well, good luck to them. I think it reveals more about that person than what the future actually holds.

Some people might suggest that this is the case, but if you look at the averages and standard deviations of returns, you can model different scenarios of what might happen, for example with a monte carlosimulation.

This is better than taking a specific figure, but it still has its limitations. For example, it generally assumes that investment returns are normally distributed. This is a big assumption, and not, to my mind, a convincing one.

Having said all this, there are things that I can say with confidence (if not absolute certainty).

For example, that investing in equities has historically generated higher returns than fixed interest over the long-run, albeit with more ups and downs (volatility). It makes sense that this trend will continue into the future.

And especially if you’re retired and will need to rely on your capital to support your lifestyle – it’s important to review your returns regularly and calibrate your lifestyle expenses to how your investments are performing.

This works both ways – whether you’re not generating the return you expected, or whether you’re generating better-than-expected returns. In the latter scenario, you might want to increase your expenditure, unless you want your children to fly first-class once you’re gone.

A couple of graphs illustrating this are below.

The following chart illustrates the same scenario as above, but with a portfolio consisting entirely of fixed interest products. Pay attention to the vertical axis relative to the other graphs. Note the highest balance at the end of 30 years is $4,902,867.

The following chart relates to the same scenario, but with a portfolio consisting entirely of equities. Pay attention to the vertical axis figures. Note the highest balance at the end of 30 years is $15,852,374.

When people ask me what sort of investment return they can expect, I wish I could give them an exact response! But the only way I’d be able to answer accurately is with hindsight. And unfortunately, I don’t have a time machine that lets me go into the future.

If the first question you ask a financial adviser is “where do you get your research from?”, it probably means you’re confusing the roles of financial advisers and investment managers. It’s an easy distinction to overlook – many financial advisers think they’re investment managers, too.

I talk briefly about CFDs or “contracts for difference” (moral of the story: steer clear!), and use CFDs to illustrate something called counterparty risk. Generally speaking, the counterparty risk with a CFD is high, and the counterparty risk with a reputable managed investment scheme is low.

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(c) 2018 Sonnie Bailey. Sonnie is an Authorised Financial Adviser - disclosure statements are available on request. All information on this site is general in nature and no substitute for personalised financial advice.